The present invention relates to a vehicle wheel end having a bi-directional overrunning clutch, and particularly a wheel end having a bi-directional overrunning clutch functioning as a hublock.
Some four-wheel vehicles are capable of being selectively switched from a condition of two-wheel drive (often referred to as xe2x80x9c4xc3x972xe2x80x9d) to a condition of four-wheel drive (often referred to as xe2x80x9c4xc3x974xe2x80x9d). Such a vehicle requires that one of the axles comprise a set of half shafts in which a hub is locked to the half shaft and receiving drive torque part of the time, but the hub may be rotationally disengaged from the half shaft at other times, during which the hubs are able to freewheel. This prevents drag and wear due to forced rotation of the drive train as a result of the front wheels being driven as the vehicle is propelled.
In a vehicle having two axles with four wheels, only one of the axles will be provided with steerable wheels. This axle is usually the axle which receives drive torque on a selective basis, the non-steerable axle normally being provided with full-time drive torque. While the technical requirements for a non-steerable, full-time-drive axle are among the least complex of the possible configurations, the combination of steerability in a selective drive axle provides a great amount of technical challenge. For that reason, among others, it is highly desirable to be able to combine and simplify structures to the fullest extent possible.
There are several devices shown in the prior art disclosing mechanisms for rotationally engaging and disengaging a hub. Many of these devices disclose locking hub clutch systems that require external actuation or control using electrical wiring, vacuum hoses, etc. One type of such a device uses a separate vacuum or pressure chamber located at the outer end of the wheel hub. The problem with these devices is that they must be attached or integrated into areas where there is little room. This may result in many other problems, from loss of control due to failure of the control mechanism, to aesthetics such as unsightly protrusions extending from the center of the wheel. One prior art device discloses a hub locking clutch device in which the locking actuator piston operates in a machined cylinder within the axle stub shaft and the axle joint yoke. In this device the cylinder and the locking actuator piston are an integral part of the axle shaft. While this device does not require attachment of a separate vacuum or pressure chamber, like the wheel end devices, the space available in the axle provides a relatively small diameter available for transmitting torque between its elements, resulting in higher stresses on its members.
In yet another device, the hub locking actuator is a hydraulically actuated ring and diaphragm which is attached to the knuckle. While this device has a much larger diameter available for transferring torque than the previous devices, it still requires the addition of a separate pressure chamber.
It is therefore an advantage of the present invention to provide a simplified version of a hub locking device.
This advantage of the present invention is achieved by an integrated wheel end assembly for a vehicle comprising a knuckle coupled to the vehicle, a bearing assembly mounted to the knuckle, a cylindrical wheel hub mounted on the bearing assembly, a stub shaft, and a bi-directional overrunning clutch member. In a preferred configuration, the wheel end assembly receives drive torque from a half shaft through a constant velocity joint. The bearing assembly allows for relatively free rotation of the wheel hub about a central axis thereof. The wheel hub has a flange for mounting the wheel at an outboard end thereof and a drive flange at an inboard end thereof. An outer circumference of the drive flange has a plurality of external teeth spaced evenly therearound. An outboard end of the stub shaft is rotatingly supported in the wheel hub and an inboard end thereof defines a housing for the CV joint. This housing has a plurality of external teeth. The housing and flange are positioned axially adjacent to each other. The bi-directional overrunning clutch member comprises two clutch plates, each having a set of internal teeth, one sized and adapted for engaging the external teeth on the housing and the other set sized and adapted for engaging the external teeth on the drive flange. In a first configuration the clutch plates are disengaged such that the rotating CV housing teeth cause only the corresponding clutch plate to rotate and no drive torque is transferred from the half shaft to the wheel hub. In a second configuration the clutch plates are engaged so as to rotate with one another and the clutch plate teeth engage both the CV housing teeth and drive flange teeth, such that drive torque is transferred from the half shaft to the wheel hub through the engagement.
It is therefore an advantage of the present invention to provide a simplified version of a hub lock assembly where the hub lock feature is automatically provided by a wheel end incorporating a bidirectional overrunning clutch. This results in less parts as well as added protection for the interior wheel elements.